This revised proposal presents an innovative, approach to cellular interactions between neural transplants and host brain and, for the first time, will attempt to compare neural transplant models in caritically important areas of brain development. This investigation will provide an original study on the alterations induced by grafts on the Blood-Brain-Barrier (BBB), one of the most basic of brain mechanisms. Using protein tracer histochemistry (HRP) and computer analysis, the extent of permeability changes will be delineated under various experiental parameters such as source of graft, age and effects of lesions. Using a graft as an indwelling portal, it will be determined for the first time that blood-borne agents, that normally do not cross the BBB, such as analogues of catecholamines, can circumvent the BBB rapidly. Future potential studies might thus include facilitation of passge of non-perm-eating agents to a local brain site, possible manipulation of the cerebrospinal fluid compartment and the potential as a model for tumor sites which lack a BBB. Using precise immunocytochemical methods to detect Glial Fibrillary Acidic Protein (GFAP), this proposal will characterize the response and directed migration of astroglia from brain to graft. Knowledge of astroglial proliferation and orientation in response to different grafts (PNS or CNS) host ages or lesions is important in understanding both a grafts' (PNS or CNS) host ages or lesions is impoatant in understanding boath a grafts' interactions with host brain and its longevity. In addition, immunochemical detection could praovide insight into the mechanisms of translocation of glial and neural tissue, perhaps after a lesion, from one part of the brain or spinal cord to another. This intergrated proppsal utilized EM cytochemistry, immunocytochemistry, fluorescence and computer analysis to study transmitter and neuropeptide production by a transplant. The hypothesis is that transmitter specific lesions are a stimulus foar grafted regenerating axons to re-innervate denervated sites, enhancing survival of foreign neurons and increasing or changing transplant produced transmitter or peptide. Experiments might make it possible to test, in the future if transplant's function can be affected by blood-borne agents or specific lesions.